Introduction: Diabetes mellitus (DM) is one of the global health emergencies that characterized by high blood glucose levels (hyperglycemia). Type 2 DM is the most common type in diabetic populations. Inhibition of alphaglucosidase can ameliorate postprandial hyperglycemia that occurs in patients with type 2 DM. Adding antioxidants to the therapy of DM is intended to reduce complications caused by oxidative stress. Some species of Garcinia have been proven to inhibit alpha-glucosidase and have antioxidant activity, but there is no research on Garcinia fruticosa Lauterb. Therefore, the aims of this research were to determine the activity of Garcinia fruticosa Lauterb. stem bark in inhibiting alpha-glucosidase and as an antioxidant. Methods: In this research, the Garcinia fruticosa Lauterb. stem bark was dried, grinded, and extracted by multistage maceration using n-hexane, ethyl acetate, and methanol. Inhibition of alpha-glucosidase test has been done in vitro on concentrated extracts and measured by microplate reader at 400 nm. The antioxidant test has been done using DPPH scavenging method and was measured by microplate reader at 519 nm. Results: Ethyl acetate extract is the most active extract for both test. IC50 values for inhibition of alpha-glucosidase test are 20.18 \μg/mL that is more active than standard (acarbose) which has IC50 value 141.55 \μg/mL. Meanwhile, IC50 value from an antioxidant test is 8.93 \μg/mL that is not more active than standard (quercetin) which has IC50 value 2.51 \μg/mL. Conclusion: Phytochemical screening shows that the ethyl acetate extract contains alkaloids, flavonoids, glycosides, saponins, and tannins.